The pair were delivering potatoes on September 24 last year when the automated barriers at Gwinear road level crossing stopped working.

After waiting in a queue of traffic for about 20 minutes, the men ignored the advice of two Network Rail maintenance workers and drove their tractors and trailers around the barriers and over the Penzance to Paddington line.

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Elaine Hobson, for the CPS, said: "They were told in the strongest of terms that it was not safe to go across the crossing.

"This is a serious and flagrant breach of what they were supposed to do and it could have had disastrous consequences as no one was aware of when a train was coming.

"This was not a minor risk but a serious one which they took that day."

Lyndel, 61, and French, 23, used the crossing about seven times a day while collecting and delivering loads of potatoes.

The defence argued that a diversion route would have taken the men through built-up areas in Hayle or Redruth.

The court also heard there were no trains scheduled at that time of the day and both drivers had an increased view of the tracks due to the height of their tractor cabs.

Judge Christopher Harvey Clark, QC, said: "I can well understand how impatient you were becoming. In the circumstances there was no risk of an accident as no trains were coming and from the vantage point of a tractor cab I am satisfied you knew no trains were coming.

"But with the barrier down you broke the law so I have to penalise you today for careless driving."

Lyndel and French were each fined £250 and ordered to pay £100 in prosecution costs and a victim's surcharge of £25.